Ingredients

In a small heavy saucepan, melt chocolate chips with water over low heat; stir until smooth. Stir a small amount of hot chocolate mixture into egg yolk; return all to the pan, stirring constantly. Cook and stir for 2 minutes or until slightly thickened. Remove from the heat; stir in vanilla. Cool, stirring several times.

In a mixing bowl, beat whipping cream until it begins to thicken. Add sugar; beat until soft peaks form. Fold in cooled chocolate mixture. Cover and refrigerate for at least 2 hours or overnight. Garnish with whipped cream if desired.